Current Limitation - Siemens 3VA1 100 A Manual

2.3.5

Current limitation

The term "current limitation" refers to the action of limiting the peak value of the prospective
impulse short-circuit current i
The compact design of the breakers has been made possible by their excellent current
limiting capabilities. In the event of a short circuit, the molded case circuit breaker
significantly reduces the magnitude of let-through current, i.e. it reduces the current loading
of downstream equipment (lower thermal load, fewer dynamic forces). The level of let-
through energy is also reduced to a considerable extent.
3VA molded case circuit breakers are designed with a current-limiting capability. IEC EN
60947-2 (VDE 0660-101), section 2.3, page 12, defines current-limiting molded case circuit
breakers in the following way:
"Circuit breaker that prevents the let-through current from achieving the prospective peak
value over a specific current range, and that limits the let-through energy (I
is lower than the let-through energy of one half-wave of the symmetrical prospective current."
①
②
③
i
D
i
p
t
a
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
p
Unlimited current
Peak value of limited current
Limited current
Let-through current
Unlimited impulse short-circuit current
Break time
to a lower let-through current i
Description
2.3 Technical details
.
D
t) to a value that
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